The proliferative retinopathy model of oxygen-induced neovascularization will be studied biochemically and histologically, using newborn and young dogs. Studies involve the isolation and purification of a possible angiogenesis factor(s) and its inhibitor(s) from vitreous and retina, and elucidation of the vasoproliferative mechanism in the retinas of the experimental model. Previous studies on the vitreal protein content raised the possibibility that the vitreal soluble proteins might be involved in process of both abnormal retinal vascularization. Studies are in progress to verify this possibility. We are developing a better, sensitive, and quantitative assay, with the fetal aortic endothelial cell culture technique, and we will further investigate our previous observation of an endothelial cell growth factor in fetal and neonatal vitreous. However, whether this growth factor is responsible for vasoproliferation in retina remains to be proven. The factor is a small molecule (less 1000), and has been purified to approximately 10-fold.